MB39A119 Datasheet, PDF (17/53 Pages) Fujitsu Component Limited. – DC/DC Converter IC of Synchronous Rectification for charging Li-ion battery

MB39A119
2. Protection Function
(1) Under voltage lockout protection circuit block (VREF-UVLO)
A momentary decrease in internal reference voltage (VREF) may cause malfunctions in the control IC, resulting
in breakdown or degradation of the system.
To prevent such malfunction, the under voltage lockout protection circuit detects internal reference voltage drop
and fixes the OUT-1 terminal (pin 27) and the OUT-2 terminal (pin 24) to the “L” level. The system restores voltage
supply when the internal reference voltage reaches the threshold voltage of the under voltage lockout protection
circuit.
Protection circuit (VREF-UVLO) operation function table
When UVLO is operating (VREF voltage is lower than UVLO threshold voltage) , the logic of the following terminal
is fixed.
OUTD
OUT-1
OUT-2
CS
VB
Hi-Z
L
L
L
L
(2) Under voltage lockout protection circuit block (VCC-UVLO, VB-UVLO)
The transient state or a momentary decrease in power supply voltage, which occurs when the bias voltage (VB)
for output circuit is turned on, may cause malfunctions in the control IC, resulting in breakdown or degradation
of the system.
To prevent such malfunction, the under voltage lockout protection circuit detects a bias voltage drop and fixes
the OUT-1 terminal (pin 27) and the OUT-2 terminal (pin 24) to the “L” level. The system restores voltage supply
when the power supply voltage or internal reference voltage reaches the threshold voltage of the under voltage
lockout protection circuit.
Protection circuit (VCC-UVLO, VB-UVLO) operation function table
When UVLO is operating (VCC voltage or VB voltage is lower than UVLO threshold voltage) , the logic of the
following terminal is fixed.
OUT-1
OUT-2
CS
L
L
L
(3) Under input voltage detection comparator block (UV Comp.)
VCC terminal (pin 1) voltage and -INC2 terminal (pin 11) voltage are compared, and VCC voltage is lower than
the battery voltage +0.1 V (Typ) and fixes the OUT-1 terminal (pin 27) and OUT-2 terminal (pin 24) to the “L” level.
The system restores voltage supply when the input voltage reaches the threshold voltage of the under input
voltage detection comparator.
Protection circuit (UV Comp.) operation function table
When under input voltage is detected (Input voltage is lower than UV Comp. threshold voltage) , the logic of the
following terminal is fixed.
OUT-1
OUT-2
CS
L
L
L
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